Epoxy resins have been widely used in electronic material fields as epoxy resin compositions combined with curing agents. Properties such as the high adhesion to a substrate, the hard-coat property, the high heat resistance, and the high transparency for visible light are required for a molding material in applications to, among such electronic material fields, for example, a high refractive index layer of an anti-refractive coating (such as an anti-refractive coating for a liquid-crystal display), an optical thin film (such as a reflecting plate), a sealant for electronic parts, a printed circuit board, and a material for an interlayer insulation film (such as a material for an interlayer insulation film for a buildup printed circuit board).
On the other hand, many studies have been carried out these days on epoxy resin compositions in which an epoxy compound is combined with a photo or thermal acid generator because the epoxy resin composition does not need a solvent and the epoxy compound can be singly cured. Particularly, photo-cationic curing by ultraviolet ray is extremely excellent in that the curing does not need a large oven for curing and an amount of energy consumption is small.
An alicyclic epoxy compound in which only an alicyclic structure has an epoxy group is widely used because it is highly reactive to cationic curing using light. However, the cured product tends to be hard and brittle because its structure is rigid.
A lactone-modified multifunctional alicyclic epoxy compound and an epoxy resin composition using the epoxy compound and a method of producing the same are disclosed (refer to Patent Document 1).
On the other hand, it has been generally considered that a glycidyl ester-based epoxy compound is not suitable for cationic curing because such an epoxy compound has low reactivity with acid generators and needs much reaction time.
As the multifunctional epoxy compounds having glycidyl ester groups, epoxy resin compositions using cyclobutanetetracarboxylic acid tetraglycidyl ester, cyclopentanetetracarboxylic acid tetraglycidyl ester, and cyclohexanetricarboxylic acid triglycidyl ester are disclosed (refer to Patent Documents 2 and 3).
A carboxy group-containing resin employing, as a crosslinkable compound, an epoxyalkyl ester of a cyclohexanedicarboxylic acid having an epoxy group is disclosed (refer to Patent Document 4).
Patent Document 1: Japanese Patent Application Publication No. 4-069360 (JP 4-069360 A)
Patent Document 2: Japanese Patent Application Publication No. 50-010893 (JP 50-010893 A)
Patent Document 3: Japanese Patent Application Publication No. 2006-274190 (JP 2006-274190 A)  Patent Document 4: U.S. Pat. No. 3,565,922 Specification